1. Field of the Invention
The present invention relates to a process for preparing an alumina composition and an alumina composition obtained by the process. More particularly, the invention relates to a carrier for a petroleum refining catalyst, an alumina composition suitable for a catalyst, a process for preparing the alumina composition, an alumina composition suitable for a monolithic molded product used for an exhaust gas purifying catalyst or an absorbent, a process for preparing the alumina composition, and a catalyst or a monolithic molded product formed from the alumina composition.
2. Background Art
It has been heretofore known to use, as an aluminum source to prepare an aqueous alumina sol, a gel obtained by hydrolysis of an aluminum salt (U.S. Pat. No. 2,915,475), metallic aluminum (Japanese Patent Publication No. 166220/1985, Japanese Patent Laid-Open Publication No. 24824/1993) or an aluminum alkoxide (Japanese Patent Publication No. 166220/1985, Japanese Patent Laid-Open Publication No. 10535/1995).
An alumina carrier for a hydrotreating catalyst used for petroleum refining is desired to be controlled in its specific surface area, pore volume and pore size distribution, and as the alumina carrier, alumina obtained from pseudoboehmite prepared by hydrolysis of an aluminum salt in an aluminum salt aqueous solution has been heretofore employed (see Japanese Patent Laid-Open Publication No. 71456/1971 and Japanese Patent Publication No. 26512/1986). In the above methods, however, there is a problem in that a large amount of energy is consumed and wastes are produced.
The present inventor has proposed before an alumina sol and a process for preparing the same (WO97/32817). By the use of this alumina sol, alumina of high specific surface area can be obtained, but it is difficult to obtain alumina of much higher specific surface area. In addition, an inexpensive aluminum source such as gibbsite cannot be used alone. On the other hand, a monolithic type catalyst carrier, that is used for a catalyst for purifying exhaust gas from a mobile generation source, needs a complicated preparation process comprising molding inert cordierite or stainless steel into a monolithic substrate and then coating the surface of the substrate with a carrier material mainly containing alumina by wash coating.